1. Field of the Invention
The present invention relates to a numerical analysis data evaluation apparatus suitably applied to a CAE (Computer Aided Engineering) system for numerically simulating a physical phenomenon based on numerical analysis using a three-dimensional shape model, and a thermal fluid pressure data evaluation apparatus using the numerical analysis data evaluation apparatus.
2. Description of the Background Art
In numerical analysis represented by a FEM (finite element method), a FDM (finite difference method) or a FVM (finite volume method), a technique of modeling an object or fluid region to be analyzed with a set of elements such as hexahedral mesh or tetrahedral mesh has been heretofore used in order to perform various kinds of analyses such as thermal fluid analysis, strength analysis, electromagnetic field analysis, acoustic analysis, etc. When the object to be analyzed is a thin plate structure, quadrilateral or triangular elements with thicknesses given as attribute values may be used. This is because the load on calculation of shell elements such as quadrilateral elements or triangular elements is lower than the load on calculation of solid elements such as hexahedral mesh or tetrahedral mesh. Because the needs of reproducing and evaluating a shape more in detail are high in practical design, a three-dimensional analysis model based on solids with thicknesses is often generated even for a shape model of a thin plate structure. In addition, the case for performing large-scale numerical analysis using a detailed three-dimensional shape model and large in the number of elements has increased in cooperation with recent improvement in computer throughput.
To evaluate various kinds of physical quantities obtained by numerical analysis, it is general that performance of each analysis model is evaluated while isosurfaces in a designated region or contour lines in a designated cross section are dialogically displayed after execution of the analysis. On this occasion, not only physical quantities are displayed simply but also the spatial average value in the designated region and the integrated value, differential value, maximum value and minimum value of each physical quantity are generally obtained. For example, the highest point of temperature and the magnitude of pressure loss are evaluated in the case of thermal fluid analysis or the place of the maximum stress is specified and evaluated in the case of strength analysis through the aforementioned process, so that such evaluation is reflected on design of various kinds of devices.
In data evaluation of numerical analysis, the difference between the physical quantity on a front surface of each member constituting an object and the physical quantity on a rear surface of the member may be obtained to evaluate the distribution of physical quantity difference values between the front and rear surfaces of the member. With respect to spatially discretized elements of a three-dimensional shape model, however, the planar position of each element on the front surface of the member is not basically coincident with the planar position of a corresponding element on the rear surface of the member. It is therefore necessary to evaluate a desired region by traversing the point of evaluation while interpolating the value of the physical quantity of at least one element on a surface. For example, it is further necessary to beforehand predetermine a rear surface-side element or element group corresponding to a certain front surface-side element. In the background art, there is an instance in which correspondence between elements with respect to a flattened member is examined in advance based on coordinate information so that a program is generated specially by use of an extended function of an analysis result processing portion of a numerical analysis apparatus to execute a procedure of processing including interpolation of physical quantities. In this method, a result of analysis can be evaluated when another analysis is executed with only change of analysis conditions (load condition etc. in the case of strength analysis, or heat value etc. in the case of thermal fluid analysis) without any change of the shape of the three-dimensional shape model.
However, when the size or structure of the three-dimensional shape model is changed largely, it is necessary to generate the program again. Although processing can be made relatively easily if the member to be evaluated is a simple flat plate, there has been heretofore no generalized method for evaluating physical quantity differences between a front surface side and a rear surface side of a three-dimensional shape model having a complicated geometry because there is an additional portion to a general structure, for example, a general structure-reinforcement rib is attached to the general structure, an assembling hole is formed in the general structure, and a concave/convex portion is partially present in the general structure.
As countermeasures, there has been proposed a technique in which a result of expression of a physical quantity distribution of a front surface side of a member in contour line etc. and a result of expression of a physical quantity distribution of a rear surface side of the member in contour line etc. are displayed side by side for the purpose of visual evaluation or physical quantities of important places on the front surface side and the rear surface side are acquired at sampling points in a range of from the order of several points to the order of tens of points to quantitatively evaluate difference values therebetween in addition to the aforementioned visual evaluation (see Yasushi Ito and Kazuhiro Nakahashi, Improvements in the reliability and quality of unstructured hybrid mesh generation, International Journal for Numerical Methods in Fluids, 2004, vol. 45, pp 79-108).
The method disclosed in the International Journal for Numerical Methods in Fluids, 2004, vol. 45, pp 79-108 has a disadvantage in that the risk of slipping over important evaluation points becomes so high that the influence of evaluating persons' individual differences on evaluation of analysis results becomes large because sampling points are determined based on evaluating persons' past experience and intuition.
Moreover, with respect to the case where a three-dimensional shell model having a thickness of zero on analysis model is used in numerical analysis, the same problem as described above still remains because an analysis result evaluation portion of the numerical analysis apparatus according to the background art has no function of calculating physical quantity differences between the front surface side and the rear surface side of elements.
Moreover, when structural examination is made for the purpose of mounting of cooling in a device, there are many instances in which a secondary flow is caused by pressure difference when pressure difference between the front surface side and the rear surface side of a partition wall member is evaluated so that an opening is provided in a place where the pressure difference between the front and the rear of the member is large. Because the secondary flow passes by a heat generating body (heat generating parts) which is a subject of cooling, cooling may be accelerated easily without addition of any cooling fan. In this case, it is necessary to perform thermal fluid analysis of the three-dimensional shape model to specify a large pressure difference place of each member and evaluate whether the secondary flow effectively contributes to cooling of the noticeable heat generating body (heat generating parts) or not, when a structure in which an opening is provided in the large pressure difference place is formed.
In the background art, there is a problem that the time required for evaluation and examination becomes considerably long because each evaluating person decides the position and size of the opening in a trial-and-error manner depending on past experience and intuition. There is another problem that the degree of final improvement in cooling performance is apt to be affected by evaluating persons' individual differences so that structural cooling performance artificially varies easily according to evaluating persons' individual differences because the aspect of depending on evaluating persons' experience is high. Incidentally, this problem can be regarded as a problem in a thermal fluid pressure data evaluation apparatus when pressure is used as the physical quantity in the numerical analysis data evaluation apparatus.